In various surgical operations, an ablation of affected parts, a repair of damaged sites and surfaces or the like is very often conducted. Especially, in the surgical operations for various organs such as the lungs, heart, liver, brain, digestive organs and gallbladder, unless the resected site or defective part of the organs or the like is replaced or repaired or augmented (i.e., compensated) with a membranous substance covering the tissue of such organs, the fundamental functions of the organ will be damaged in many cases. If the treatment is not completely performed, the patient will die due to a malfunction of the organ or, even if the patient passes the crisis, an often observed tendency is that the prognosis is quite bad. Also, with respect to an insufficient suture fixation of the membranous substance in a prosthetic or compensated part, even if the function of the treated organ itself manages to be maintained, body fluids, digestive juices or contents which are exuded or leak from the organ may cause infection, or cause an attack or an erosion of other organs to eventually jeopardize life.
Further, there happens highly frequently an adhesion of the membranous substance at these prosthetic or compensated parts, and consequently, a malfunction of the organ may be induced in the course of time. In order to solve such problems, membranous substances or adhesion-preventing membranes made of various materials have been developed to cover the organ or the tissue of the organ.
Conventionally, a surgical wound dressing material is known in which a non-woven fabric layer made of collagen fibers is treated with aldehydes to have water resistance and the fibers are bonded mutually with collagen (Japanese Unexamined Patent Publication No. 141190/1975). However, because the surface of the dressing material is treated with a cross-linking agent, the material has inferior biocompatibility or is inferior in guiding tissue regeneration. Further, it is uncertain whether the dressing material can function to have sufficient suture strength or prevent an adhesion of a wound although it covers the wound.
In the above conventional technique, the adhesion-preventing membrane exhibits insufficient adhesion-preventing effects, suture strength, biocompatibility and decomposition and absorption capability in a living body, and particularly, the membrane can not simultaneously exhibit these characteristics. Therefore, the aim of the present invention is to resolve simultaneously the conventional problems of adhesion-preventing membranes that include insufficient suture strength, insufficient biocompatibility or decomposition and absorption capability in a living body, and insufficient adhesion-preventing effects as well.
The present inventor has already proposed as an improved medical membrane utilizing only animal collagen, a medical collagen membrane of non-woven fabric layer which comprises cross-linked collagen in which at least one surface of a membrane is covered with a collagen coating (Japanese Patent Application No. 264891/1998). Because the surface of the membrane is not cross-linked with a cross-linking agent, the membrane is superior in biocompatibility, guiding tissue regeneration and the like as compared to a surgical wound dressing material in which a non-woven fabric layer made of collagen fibers is treated with aldehydes to have water resistance and the fibers are bonded mutually with collagen (Japanese Unexamined Patent Publication No.141190/1975). Also, another characteristic of the membrane is to have a wide variety of applications for surgical procedures as in, particularly, compensation or prothesis of various organs, since the membrane can be fixed directly to the organs by means of a suture. Additionally, the membrane especially has strength enough to withstand suture fixation compared to a patch for visceral surgery which is comprised of two layers of (1) porous fibrous collagen layer and (2) collagen and/or a gelatin membrane (Japanese Patent No. 2775115). Therefore, it is possible for the membrane to be fixed more firmly to application sites with a general and inexpensive surgical suture thread as compared to fixation with only a biological adhesive, and a wide range of surgical applications are characteristically provided.
However, the above improved membrane has a difficulty in obtaining a sufficient adhesion-preventing property because the raw material of the membrane is collagen derived from an animal, which promotes adhesion, proliferation and extension of cells. Therefore, it is an object of the present invention to provide a suturable and adhesion-preventing membrane for guided tissue regeneration which is superior in suture strength, biocompatibility and guiding tissue regeneration, and further has an adhesion-preventing property.